Vascular endothelial growth factor expression by hyalocytes and its regulation by glucocorticoid.
OBJECTIVE
Tumour necrosis factor-alpha (TNF-alpha) is one of the major inflammatory cytokines involved in the pathogenesis of various vitreoretinal diseases. The authors investigated the effect of hypoxia, TNF-alpha and dexamethasone on vascular endothelial growth factor (VEGF) expression by cultured hyalocytes.


METHODS
Hyalocytes were isolated from bovine vitreous. Hypoxic and TNF-alpha-dependent effects on cultured hyalocytes were investigated using several assays to determine VEGF protein expression, hypoxia-inducible factor (HIF)-1alpha protein levels, HIF-1alpha-DNA-binding ability and VEGF mRNA stability. The effects of dexamethasone on VEGF expression and its intracellular signalling under hypoxic or TNF-alpha stimulated conditions were also examined.


RESULTS
Hypoxic conditions and TNF-alpha stimulation induce VEGF expression in hyalocytes. These stimuli also stabilise HIF-1alpha protein and increase its DNA-binding ability. Dexamethasone significantly inhibits both HIF-1alpha protein levels and HIF-1alpha-DNA-binding activity, and also decreases the hypoxic- and TNF-alpha -dependent induction of VEGF expression in hyalocyte. However, dexamethasone has no significant effect on the stability of VEGF mRNA.


CONCLUSIONS
Hyalocytes may be involved in various vitreoretinal diseases by increasing HIF-1alpha protein stability and HIF-1alpha-DNA binding, and thus increasing VEGF production under pathological conditions. Dexamethasone seems to be capable of inhibiting hypoxic and TNF-alpha dependent VEGF production, presumably via its inhibitory effects on HIF-1alpha protein levels and its DNA-binding activity.
Hata
Y
Y
Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. hatachan@med.kyushu-u.ac.jp
Sassa
Y
Y
Kita
T
T
Miura
M
M
Kano
K
K
Kawahara
S
S
Arita
R
R
Nakao
S
S
Shih
J L
JL
Ishibashi
T
T
D000818:Animals; D002417:Cattle; D015687:Cell Hypoxia / Q000187:drug effects* / Q000502:physiology; D004247:DNA / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005938:Glucocorticoids / Q000494:pharmacology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D014822:Vitreous Body / Q000166:cytology*
D005938:Glucocorticoids; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; D003907:Dexamethasone; D004247:DNA